Investigation Of Magnetic Properties For NiMgCuZn Ferrites Synthesized By NaOH Co-precipitation Method

As an important surface mount device (SMD), multilayer chip inductors (MLCI) has developed rapidly in recent years and are widely used in information industry, aerospace, military and national defense fields. Up to now, low temperature sintered NiCuZn ferrites have been the dominant materials for MLCI due to its better magnetic properties and low sintering temperature and it has become one of the hot researching focus in the magnetic material field. At the same time, because of the high resistivity, low magnetostriction coefficient, good environmental stability and low cost., MgCuZn ferrite is also a potential magnetic material for wide applications in multilayer chip inductors (MLCI).In this dissertation, we used analytical grade nickel nitrate [Ni(NO3)2·6H2O] magnesium nitrate [Mg(NO3)2·6H2O], zinc nitrate [Zn(NO3)2·6H2O], copper nitrate [Cu(NO3)2·3H2O] and iron nitrate [Fe(NO3)39H2O] as the raw material, and prepared NiMgCuZn ferrites by NaOH chemical co-precipitation method. We mainly investigate the effect of the calcining temperature and Mg substitution on structure and magnetic properties of the Ni0.25Cu0.3Zno.45Fe204ferrites by using the technology of X-ray diffractometer (XRD), Vibrating sample magnetometer (VSM), HP4194A impedance analyzer and mission scanning electron microscopy (FESEM, JEOL JSM-6700F, Japan). The influence mechanisum were discussed carefully.The Ni0.15Mgo.iCu0.3Zn0.45Fe204ferrites have been synthesized by chemical coprecipitation with calcining temperature at500-800℃. The X-ray diffraction patterns of these ferrites confirmed the formation of the single phase spinel structure. And the crystallite size of the calcined ferrite powder increased from12.3nm up to36.2nm with calcining temperature. The calcining temperatures had obvious influence on the bulk density and the grain size. But, no distinct differences were obtained for Curie temperature. When the calcining temperature is600℃, the sample showed the highest initial permeability and saturation magnetization. It is certain that the calcining temperature of600℃is the optimum temperature owing relatively good properties. Moreover, with the calcining temperature at500℃and600℃, the saturation magnetization of the calcined ferrite powder is lower than that of bulk ferrite, but when the calcining temperature is above700℃, bulk ferrite has the larger saturation magnetization compared to the powder ferrite. Ni0.25-xMgXu0.3Zno.45Fe204(for x=0,0.05,0.1,0.2and0.25) ferrites have been synthesized by NaOH co-precipitation method. All the samples have been confirmed to form the cubic spinel structure of single-phase. The lattice constant was found to increase with Mg content. The bulk density decreases with increasing Mg concentration. And scanning electron microscope micrographs show no obvious differences among all samples with different Mg concentration. With Mg content increasing, the initial permeability monotonously increases while the cut-off frequency gradually decreases, which agrees well with Snoek’s law. The saturation magnetization and the Curie temperature continuously decrease with Mg content increasing, and the saturation magnetization of bulk ferrite the is larger than that of calcined ferrite powder. But no noticeable variation of quality factor with Mg content is observed. Synthetically, x=0.1is the optimum Mg content in our study, the Ni0.25Mgo.iCu0.3Zno.45Fe204sample possesses relatively high μi’and good temperature stability, and at the same time, the sample maintains the moderately high Ms,Tc,fr and PB.